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        <meta charset="UTF-8"/>
        <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
        <meta http-equiv="X-UA-Compatible" content="ie=edge"/>
        <title>Document</title>
        <script>
            /* 
                const 声明变量，变量值只能在声明的时候确定，后续是没有办法修改的。
                【注】const声明常量(变量没有办法改);
             */
             const IP = "10.30.152.33";

             alert(IP);
             IP = 'xx';
             alert(IP);

        </script>
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    <body>
        
    </body>
</html>